Rookie here, but when do we typically see rating changes? After promotion, at the end of the season, end of spring training? I do not believe I saw any rating changes post spring training, but just curious when I should be on the lookout. Thanks.

You'll see ratings updates at the end of spring training, and then again 4 or 5 times throughout the regular season. Maybe every 30-40 games or so.

Other than the ST updates, which come immediately after ST, the other ones don't necessarily come all at the same time.

You'll also get some that coincide with promotions (not always), demotions (not always), trades, injuries, and injury recovery.